Rhizosphere Tripartite Interactions and PGPR-Mediated Metabolic Reprogramming towards ISR and Plant Priming: A Metabolomics Review

Abstract

Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms colonising the rhizosphere. PGPR are involved in plant growth promotion and plant priming against biotic and abiotic stresses. Plant–microbe interactions occur through chemical communications in the rhizosphere and a tripartite interaction mechanism between plants, pathogenic microbes and plant-beneficial microbes has been defined. However, comprehensive information on the rhizosphere communications between plants and microbes, the tripartite interactions and the biochemical implications of these interactions on the plant metabolome is minimal and not yet widely available nor well understood. Furthermore, the mechanistic nature of PGPR effects on induced systemic resistance (ISR) and priming in plants at the molecular and metabolic levels is yet to be fully elucidated. As such, research investigating chemical communication in the rhizosphere is currently underway. Over the past decades, metabolomics approaches have been extensively used in describing the detailed metabolome of organisms and have allowed the understanding of metabolic reprogramming in plants due to tripartite interactions. Here, we review communication systems between plants and microorganisms in the rhizosphere that lead to plant growth stimulation and priming/induced resistance and the applications of metabolomics in understanding these complex tripartite interactions.

Untargeted metabolite profiling to elucidate rhizosphere and leaf metabolome changes of wheat cultivars (Triticum aestivum L.) treated with the plant growth-promoting rhizobacteria Paenibacillus alvei (T22) and Bacillus subtilis

“…Plant growth-promoting rhizobacteria (PGPR) form the majority of free-living beneficial bacteria inhabiting the rhizosphere. The proximity of these microbes to the plant root system allows them to establish a mutual symbiotic relationship with the associated plant through biochemical communications ( Grobelak et al, 2015 ; Mishra and Arora, 2017 ; Mhlongo et al, 2020 ; Mashabela et al, 2022a ). The rhizosphere, as such, functions as the epicenter for biochemical signaling linking the PGPR and the associated plant roots.…”

“…In return, the PGPR produces and secretes plant-beneficial compounds (i.e., siderophoses, lipopeptides, and phytohormones) essential for defense signaling and plant growth promotion ( Mus et al, 2016 ; Mhlongo et al, 2018 ). Mashabela et al (2022a) highlights the modes of action plants use to recruit beneficial bacteria with the use of root exudates, where the types of exudates released by the plant may be dependent on the current nutritional or defense requirements of the plant and thus selectively populating the rhizosphere with the PGPR fit for utilization.…”

Role of Promising Secondary Metabolites to Confer Resistance Against Environmental Stresses in Crop Plants: Current Scenario and Future Perspectives

“…In plants under abiotic stress, metabolomics is utilized to detect and/or quantify main and secondary stress-responsive compounds ( Isah, 2019 ). To study metabolic reprogramming in plants under abiotic stress, two primary techniques, i.e., non-targeted and targeted are utilized ( Mishra et al, 2015 ; Mashabela et al, 2022 ). Non-targeted metabolomics give a broad picture of the most abundant metabolites in plants under a variety of stress conditions.…”

Metabolomics and Chemoinformatics in Agricultural Biotechnology Research: Complementary Probes in Unravelling New Metabolites for Crop Improvement

“…Phenylpropanoids are essential for lignin biosynthesis and cell-wall strengthening. These compounds, thus, assist plants in formulating a solid cell-wall defence to ward off pathogenic attacks [ 73 ].…”